The conference organiser, Katina Michael, an associate professor in the school of information systems and technology at Wollongong, predicts RFID technology - implanted or worn - will become part of daily life.

In the US, VeriChip Corporation has approval from the Food and Drug Administration to implant microchips in humans. Its chips hold a 16-digit number that can link with medical records to identify an Alzheimer's patient who has become lost or warn that an unconscious patient is allergic to penicillin.

Dr Michael acknowledges RFID chips bring benefits and admires Mr Graafstra's ingenuity, but she points out that he alone decides how his chip is used. She harbours concerns that microchips implanted by corporations offer little control for other implantees, particularly chips capable of storing greater amounts of information.

Unlike Mr Graafstra, she says, people who have been chipped may have little say about what data is collected and how it is used. And recently, concerns have emerged that a coating on microchips could prove cancerous.

''The dangers definitely outweigh the benefits with regard to commercialised applications,'' she says.

''When we're talking about opting in to an application such as an implant from a commercial vendor, you've lost your freedom.''